A catboat is a single-masted vessel with a sail plan that is fore-and-aft rigged, meaning the sails are set along the line of the keel rather than perpendicular to it. A SLOOP is also a single-masted vessel, but it has two headsails in addition to its mainsail. A CUTTER is a single-masted vessel with two or more headsails and a mainsail, and is typically smaller than a SLOOP. All three of these vessels are single-masted, meaning they have only one mast.